Spectrophotometers are conventional laboratory instruments which are used for analyzing liquid samples by transmitting a light beam of known wavelength and intensity through the sample. This is important in tests such as colorimetry, fluorolumenescence, and turbidimetry.
The amount of light absorbed, transmitted, reflected or emitted by the sample is instructive of the physical properties and the concentrations of the sample's chemical components.
In a typical spectrophotometer, a liquid sample is placed in a special sample cell which has walls of transparent material (such as glass). The sample cell is then inserted into a sample cell receiver or holder in the spectrophotometer, after which a light beam is directed through the sample cell. The amount of light absorbed by the sample can be correlated to the concentration of a particular or selected chemical species in the sample. In order to conduct an analysis of another liquid sample, it is necessary to remove the first sample and insert the new sample.
There have previously been used certain spectrophotometers commercialized which include or utilize multiple sample cells. For example, U.S. Pat. No. 5,059,025 describes a movable sample cell holder which can hold several sample cells. The linear holder is moved laterally in order to position successive sample cells in the light beam so that a reading can be taken for each sample cell.
Linear sample positioners require a compartment length at least twice that of the linear sample cell holding cassette. This tends to limit the number and size of samples or increases the footprint of the sample compartment. Row by column designs add more samples at the expense of increased mechanical complexity.
Linear cartridges may become difficult to handle without touching optical faces of the sample cells and tend to be easily tipped over when laid on the work area due to their long, narrow design. Handling is further comprised since samples are packed close together to optimize use of available length.
Cell holders are generally made of metallic materials which are heavy, sensitive to chemical attack, easily bent and misaligned during handling. Sample holders for test tubes are often avoided due to the optical distortion problems created by the test tubes' lens effect.
Prior art adapters are generally designed as modifications to standard instruments. As such they are delicate and unprotected mechanisms when removed from the instrument enclosure, with the expectation that there will be few instances of replacement with different modifying elements. Testing samples in other formats is thus discouraged due to the time and skill required to change and replace sample adapters.
Previously available spectrophotometers which involve more than one sample module require additional tools, instructions or skills in order to replace one module with another, and they may require further manipulation of the hardware, software, mechanical or electrical connections in order to make these changes. This is cumbersome. Unused modules must be stored in protective boxes, cabinets or containers to protect them from dust, spills, breakage, etc. Also, assembly and disassembly exposes sensitive components to misalignment, lost hardware, fouled connectors, fingerprints on optics, etc. Further optical alignment, software and/or mechanical set up and/or calibration procedures are frequently required before sampling can begin.
There has not heretofore been provided a spectrophotometer having the features and advantages provided by the present invention.